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Trans Swap Question

Justin Fleming

Justin Fleming

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would a 700r4 trans from a 1986 k5 work in a 1990 k5. Is this a clean one for one swap?

thanks in advance
 
I believe the (Np241) transfer case had an electric speedometer output. But when they upgraded the 700r4 to electronic shift they changed it's name to 4L60E.
 
The 1990 model uses different electronics internally than the 1986 Carb model. You can, however, swap electronics between the two. The 1986 lacks the better input and low sprag of the later models as well as the auxilliary valve body system and other durability upgrades.
 
Only potential issue I am aware of would be how lockup was controlled. Internally it might all be the same, I don't know, but the 1990 would have been locked up via ECM, the 1986 via the vacuum switch setup.

Edit: I was hoping Greg would comment, this is what happens when you wait too long to respond to an open window. :)
 
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Thanks

Just wanted to say thanks for all the "knowledge Bombs" that is why this forum is so great!!!
 
Greg Ducato said:
The 1990 model uses different electronics internally than the 1986 Carb model. You can, however, swap electronics between the two. The 1986 lacks the better input and low sprag of the later models as well as the auxilliary valve body system and other durability upgrades.
Click to expand...

I dont remeber any electronic or vaccum hook up switches on my 86. I am certain its not the original trans to begin with. How can I identify the trans that is in it and what it really is from or for? I am 100% sure it is a 700R4. Also now that I think about it I beleive there is a electric square connector on the same side as the govener but I dont beleive anythign is hooked up to it....
 
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The only electronics going to the trans should be that plug which controls torque convertor lockup. You don't REALLY need to hook it up but it's better if you do. It should work just fine. You might want to verify that the TV cable is the same length for the two trucks since one is carb'd and one TBI. They should be the same with the same throw and geometry but I truly don't have that answer.
 
xenomarine said:
The only electronics going to the trans should be that plug which controls torque convertor lockup. You don't REALLY need to hook it up but it's better if you do. It should work just fine. You might want to verify that the TV cable is the same length for the two trucks since one is carb'd and one TBI. They should be the same with the same throw and geometry but I truly don't have that answer.
Click to expand...


If you do any amount of highway driving you'll want to make sure it's hooked up, otherwise the trans could run hot. You'll definitely want to reset the TV cable. Should be a direct swap.
 
Running it in OD without lockup will burn it up about as quick as running it without the TV cable hooked up. It will overheat with a quickness.
 
Justin Fleming said:
I dont remeber any electronic or vaccum hook up switches on my 86. I am certain its not the original trans to begin with. How can I identify the trans that is in it and what it really is from or for? I am 100% sure it is a 700R4. Also now that I think about it I beleive there is a electric square connector on the same side as the govener but I dont beleive anythign is hooked up to it....
Click to expand...

On the passenger side, rear corner of the trans, just above the pan gasket, facing the passenger side frame, is a raised boss on the case. There are a series of stamped letters and numbers on the pad which will identify the trans. And yes, you will need lockup to keep the trans cool and lubed in overdrive and set the tv cable correctly.
 
Trans Numbers

So my trans has a 7TKM097C and another trans I have is 7TXM105A

All I can find is this is a 1987

Can anyone tell me what the TKM and TXM model was and or any additional information based on the number listed above

thanks
 
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The 7TXM is a 5.7 model but both are virtually identical internally so just choose the cleaner of the two. Both are the preferable 87-92 variety
 
Greg Ducato said:
The 7TXM is a 5.7 model but both are virtually identical internally so just choose the cleaner of the two. Both are the preferable 87-92 variety
Click to expand...

A tranny rebuild guy was saying that there was something not so desirable about the 87 valve body. Not exactly sure what it was. Something that was changed in the later 87 models...
 
There are slight variations in all the 700 valve bodies and separator plates in the 87-91 range and of course, previous years as well. There is nothing about an 87 model which prevents it from being built and modified into a very reliable unit.
 
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